A genetic test may identify a hereditary predisposition to breast cancer. The most common of these syndromes is Hereditary Breast and Ovarian Cancer (HBOC) which causes an increased risk to develop breast, ovarian and other cancers. Other rare cancer syndromes that also cause and increased risk of breast cancer are LiFraumeni syndrome, Cowden syndrome, Ataxia Telangiwctasia, and Peutz-Jeghers syndrome. These syndromes account for less than five per cent of hereditary breast cancer.
Genetic testing is performed by a blood test that looks closely at the BRCA1 and BRCA2 genes for the presence of mutation and can identify if an individual has HBOC. This test may detect a mutation that could explain the cancer in your family. Eligibility for genetic testing is determined by the characteristics of your family history of cancer and your personal history. Your eligibility can be assessed through a discussion with the genetic counsellor in our clinic.
Genetic testing usually involves:
- A pre-test counselling session
- Informed consent and blood drawing
- Results session
- Follow-up visit(s) commencing soon after the Results Session to help with ongoing management issues for mutation carriers.
- Referrals to other health professionals as appropriate
Genetic testing is a two-step process. The initial step involves the attempt to identify an inherited predisposition to breast and ovarian cancer within a family. This is usually done by looking for mutations in the BRCA genes from a blood sample from someone in your family that has had a breast or ovarian cancer diagnosis.
If this step does not reveal a mutation, and you have a strong family history, then we consider this to be an uninformative result. This is due to the fact that there may be mutations in BRCA1 and BRCA2 that we cannot presently detect, or that there is additional breast cancer susceptibility genes that have not yet been identified.
If the initial step DOES reveal a mutation, then an inherited predisposition to breast and ovarian cancer is said to exist within the family. Other blood relatives may now proceed to the second stage of genetic testing. This stage is called the predictive testing stage. Since the mutation in the family is now known, any other blood relative may have their blood tested for the presence or absence of the mutated gene. Carriers will be at an increased risk for cancer and non-carriers will not.
The decision to participate in genetic testing is often a complicated one. Discussions with our team will give you the information you need to help you reach a decision about whether or not to proceed. The following are some testing-related issues that you may wish to think about and discuss with the genetic counsellor at your appointment.
- Genetic testing may help you better understand why cancer has occurred in yourself or other family members.
- Genetic testing may change the way you are presently screened for cancer.
- Preventive options, such as preventive surgery or chemoprevention, may be available to you that were previously unavailable.
- Genetic testing results you receive may have an impact on other family members. Some may be interested in receiving this information and others may not. This is something you may wish to explore with other family members before receiving your test results.
- Some individuals may find it distressing to know they carry a mutated BRCA gene. This feeling is normal. You might want to know what services are available to help you deal with that distress here at the Marvelle Koffler Breast Centre.
- We may ask you to participate in additional research projects that we are conducting.
- There may be issues of insurance discrimination for those with a positive test result.
- In some situations genetic testing will not help us to understand the cause of your family history of cancer.
- Genetic testing may help to clarify your cancer risk